function Headers (req, res, next) {
	//设置允许跨域的域名，*代表允许任意域名跨域
	res.setHeader("Access-Control-Allow-Origin","*");
	//允许的header类型
	res.setHeader('Access-Control-Allow-Headers', 'Content-Type, Content-Length, Authorization, Accept, X-Requested-With , yourHeaderFeild, Tk-xs');
	//跨域允许的请求方式 
	res.setHeader("Access-Control-Allow-Methods","DELETE,PUT,POST,GET,OPTIONS");
	if (req.method.toLowerCase() == 'options')
	    res.sendStatus(200);  //让options尝试请求快速结束
	else
	  next();
}
module.exports = Headers